© 2017. Published by The Company of Biologists Ltd | Journal of Experimental Biology (2017) 220, 582-587 doi:10.1242/jeb.151019
RESEARCH ARTICLE
Living in flowing water increases resistance to ultraviolet B
radiation
ABSTRACT
Ultraviolet B radiation (UV-B) is an important environmental driver that
can affect locomotor performance negatively by inducing production
of reactive oxygen species (ROS). Prolonged regular exercise
increases antioxidant activities, which may alleviate the negative
effects of UV-B-induced ROS. Animals naturally performing exercise,
such as humans performing regular exercise or fish living in flowing
water, may therefore be more resilient to the negative effects of UV-B.
We tested this hypothesis in a fully factorial experiment, where we
exposed mosquitofish (Gambusia holbrooki) to UV-B and control (no
UV-B) conditions in flowing and still water. We show that fish exposed
to UV-B and kept in flowing water had increased sustained swimming
performance (Ucrit), increased antioxidant defences (catalase activity
and glutathione concentrations) and reduced cellular damage (lipid
peroxidation and protein carbonyl concentrations) compared with fish
in still water. There was no effect of UV-B or water flow on resting or
maximal rates of oxygen consumption. Our results show that
environmental water flow can alleviate the negative effects of UV-Binduced ROS by increasing defence mechanisms. The resultant
reduction in ROS-induced damage may contribute to maintain
locomotor performance. Hence, the benefits of regular exercise are
‘transferred’ to improve resilience to the negative impacts of UV-B.
Ecologically, the mechanistic link between responses to different
habitat characteristics can determine the success of animals. These
dynamics have important ecological connotations when river or
stream flow changes as a result of weather patterns, climate or human
modifications.
KEY WORDS: Reactive oxygen species, Exercise, Locomotion,
Antioxidants, Habitat modification
INTRODUCTION
UV-B is a ubiquitous environmental driver that can damage
proteins, DNA and membranes directly (Bancroft et al., 2007), or by
inducing excessive production of reactive oxygen species (ROS)
(Kulms et al., 2002; Lesser, 2006). Oxidative damage to membranes
and proteins occurs when ROS production outpaces the capacity of
cellular antioxidant defences (Constantini, 2014; Lesser, 2006).
UV-B-induced ROS damage to muscle proteins results in impaired
locomotor performance (Ghanizadeh Kazerouni et al., 2015, 2016).
Physical activity increases ROS production by contracting muscle
acutely (Powers and Jackson, 2008). However, chronic low- to mid-
level physical activity (exercise) increases antioxidant defences,
such that oxidative stress is reduced with chronic exercise (Gram
et al., 2015; Radak et al., 2013). Defences against oxidative stress in
muscle include enzymatic antioxidants like superoxide dismutase
(SOD) and catalase (CAT), and non-enzymatic ROS scavengers
such as glutathione (GSH; Sen, 1995; Steinbacher and Eckl, 2015).
SOD converts the superoxide anion to hydrogen peroxide, which is
converted to water and oxygen by glutathione peroxidase and CAT
(Lesser, 2006). It is possible that the increased antioxidant capacity
resulting from exercise also contributes to the reduction of UV-Binduced ROS damage to muscle and mitochondria.
Exercise is defined as movement that increases energy
expenditure above basal levels (Booth et al., 2012), and which
leads to a training effect that includes increased metabolic capacities
and muscle contractile function (Davison, 1997; Gundersen, 2011;
Korzeniewski and Rossiter, 2015). In a natural context, exercise
is necessary for fitness-related activities such as behavioural
interactions, dispersal and predator–prey interactions (Irschick and
Garland, 2001; Martin et al., 2015; Sinclair et al., 2014). UV-Bmediated oxidative damage to muscles and the resulting decreases
in locomotor performance therefore can have far-reaching
ecological consequences. However, the effect of UV-B may be
habitat specific, and habitats that require high levels of physical
activity may confer protection against ROS damage via the
protective effects of exercise. In aquatic systems, water flow is a
physical factor that increases the requirement for increased
locomotor activity, which in turn can increase metabolic rate and
locomotor performance because of training effects (Dalziel et al.,
2015; Davison, 1997). It is possible, therefore, that fish living in
flowing water also have increased antioxidant activities, which
would increase resilience to UV-B-induced ROS damage compared
with fish living in still water environments.
The aim of this study was to test whether mosquitofish
(Gambusia holbrooki) living in flowing water are more resilient to
the effects of UV-B compared with animals living in still water. We
hypothesised that fish from flowing water have higher swimming
performance and metabolic scope than fish in still water, which is
paralleled by greater antioxidant capacities and lower ROS-induced
damage in response to UV-B exposure. To test our hypothesis, we
exposed fish to different levels of UV-B and water flow in a fully
factorial design.
MATERIALS AND METHODS
Study animals
1
School of Life and Environmental Sciences A08, University of Sydney, Sydney,
NSW 2006, Australia. 2School of Biological Sciences, University of Queensland,
St Lucia, QLD 4072, Australia.
*Author for correspondence ([email protected])
F.S., 0000-0002-2281-9311
Received 6 October 2016; Accepted 24 November 2016
582
All experiments were carried out with the approval of The
University of Sydney Animal Ethics Committee (approval number
L04/1-2013/3/5907). Adult male mosquitofish (Gambusia
holbrooki Girard 1859; mean±s.e.m. standard length 20.4±
0.22 mm) were collected from the field in Australia (33°46′33″S,
151°14′52″E) and kept in plastic tanks (645×423×276 mm) at a
density of 1–2 fish per litre for 1–2 weeks before starting
Journal of Experimental Biology
Ensiyeh Ghanizadeh-Kazerouni1, Craig E. Franklin2 and Frank Seebacher1,*
RESEARCH ARTICLE
Journal of Experimental Biology (2017) 220, 582-587 doi:10.1242/jeb.151019
Swimming performance
CAT
GSH
MDA
Ṁ O2
PC
ROS
SOD
Ucrit
UV-B
catalase
glutathione
malondialdehyde
metabolic rate
protein carbonyl
reactive oxygen species
superoxide dismutase
critical sustained swimming speed
ultraviolet B radiation
experiments. Fish were kept at 20°C during all procedures,
which was similar to the temperature at their collection site.
The photoperiod was 12 h light:12 h dark for all treatments,
and fish were fed twice per day with fish flakes (Wardley
Tropical Fish Flakes, The Hartz Mountain Corporation, Secaucus,
NJ, USA).
Experimental design and treatments
Fish were allocated randomly to one of four treatments: UV-B and
no UV-B control, each in still and flowing water. Fish were exposed
to treatments for 2–3 weeks. Within treatments, fish were dispersed
across three circular tanks (180 mm height and 350 mm diameter;
N=13 fish per tank), with a plastic cylinder (180 mm
height×100 mm diameter) fixed at the centre of each tank to
create an annulus that facilitated water flow (see below).
Fish in the UV-B treatment were exposed to visible light plus
UV-B, while the control groups received visible light only. UV-B
was provided by 120 cm UV-B fluorescent tubes (UVB-313 EL,
Q-lab, Cleveland, OH, USA; 280–390 nm) for 3 h each day from
11:00 h to 14:00 h, which coincides with the time of greatest
natural UV-B irradiation in the field. The natural dose of solar
UV-B radiation in summer is 7.4 W m−2 at midday at the
collection site (Ghanizadeh Kazerouni et al., 2016), with a total
ambient daily dose of 5100 J m−2 (Beckmann et al., 2014). Our
UV-B lamps were set up to generate a peak irradiance of
3.3 W m−2 at the water surface, which is equal to a total daily
dose of 1188 J m−2. We chose this lower than maximum ambient
dose of UV-B to better reflect the average conditions (Ghanizadeh
Kazerouni et al., 2016).
Water flow was generated by a submersible pump (5 W, SP-900;
Resun, China) mounted close to the wall of each tank. The pumps
created a water flow of 6–8 cm s−1 [equivalent to 3–4 body lengths
per second (BL s−1), measured with a flow meter; DigiFlow
6710 M, Savant Electronics, Taichung, Taiwan]. We chose this flow
rate because it is naturally encountered by mosquitofish (Pyke,
2005) and because it increases sustained swimming performance in
this species (Sinclair et al., 2014). Still water tanks were set up
identically except that there was no water flow.
In a preliminary experiment, we filmed the behaviour of fish (not
elsewhere used in the experiment) to ascertain that individuals in the
flow tanks experienced a greater level of (swimming) exercise
compared with fish in the still water treatment. Briefly, we filmed
(C910 camera, Logitech, Japan, filming at 30 frames s−1) fish in six
tanks each for the flowing and still water treatment. We filmed fish
every 2 h during a day, and determined tailbeat frequencies as an
indicator of swimming activity of five randomly chosen fish per
tank (Tracker Video Analysis and Modeling Tool, Open Source
Physics, www.opensourcephysics.org). Fish had a mean±s.e.m. of
7.87±0.15 tailbeats s−1 in the flowing water tank and 0.75±
0.10 tailbeats s−1 in the still water treatment.
Critical sustained swimming speed (Ucrit) was measured in 12 fish
from each treatment according to published protocols (Hammill
et al., 2004; Seebacher et al., 2015). Ucrit was measured in a Blazkastyle flume consisting of a cylindrical clear Perspex flume (150 mm
length and 38 mm diameter). The flume was fitted tightly over the
intake end of a submersible pump (12 V DC, iL500, Rule,
Hertfordshire, UK) and a bundle of hollow straws at the inlet end
of the flume helped maintain laminar flow. The flume and pump
were submerged in a plastic tank (645×423×276 mm). A variable
DC power source (NP9615, Manson Engineering Industrial, Hong
Kong, China) was used to control flow speed in the flume by
changing the voltage input into the pump. A flow meter (DigiFlow
6710M, Savant Electronics, Taichung, Taiwan) connected to the
outlet of each pump was used to measure water flow in each flume in
real-time. Fish swam at an initial flow rate of 0.06 m s−1 for 20 min.
The flow speed was then increased by 0.02 m s−1 every 5 min until
the fish were exhausted and could not hold their position in the water
column any longer. We stopped the flow for 5–10 s when fish
stopped swimming and fell back onto the grid, before increasing the
speed to the previous setting again. The trial was terminated after
fish stopped swimming for the second time. Ucrit is reported as
BL s−1.
Oxygen consumption
We determined resting and maximum rates of oxygen consumption
in 8–10 fish from each treatment. Individual fish were placed inside
respirometers consisting of cylindrical clear plastic tubes (15 mm
diameter and 100 mm length, 27 ml volume). A peristaltic pump
(i150, iPumps, Tewkesbury, UK) circulated water through the
respirometers while fish were resting. To determine resting
metabolic rate, oxygen concentration inside the respirometers
was measured with a sensor spot (PSt3, PreSens, Regensburg,
Germany) attached to the inside of the tube. Fibre optic cables
connected to an oxygen meter (Witrox, PreSens) were used to
monitor the sensor spots. The respirometers were placed in
temperature-controlled water baths, and fish were left undisturbed
inside for 2 h before measurement of resting oxygen consumption
rate (a period sufficient to achieve resting levels; Seebacher et al.,
2016). After 2 h, the pump was switched off remotely to stop the
water flow and thereby seal the respirometers without disturbing the
fish. The dissolved oxygen concentration inside the respirometers
was recorded for 15–20 min, and the slope of oxygen depletion was
used to calculate resting metabolic rate.
Maximum rates of oxygen consumption were measured in each
fish following measurement of resting oxygen consumption and
according to a published protocol (Seebacher et al., 2013). Fish were
placed in a cylindrical glass respirometer (120 ml volume), which
was placed on a magnetic stirring plate. A sensor spot (PSt3,
PreSens) was attached to the inside of the glass respirometer and
oxygen concentration was monitored by fibre optic cables
connected to an oxygen meter (FIBOX 3, PreSens). A magnetic
stir bar at the bottom of the respirometer (separated from the fish
using a plastic mesh) created water flow. A plastic column was
suspended from the lid at the centre of the respirometer to help
reduce turbulence. The flow speed was controlled by changing the
speed of the stir bar. Speed was increased until the fish could not
hold their position in the water column; it was then reduced until the
fish could keep their position in the water column and swim steadily.
This swimming speed was defined as near-maximum swimming
speed. Fish were swum at maximum swimming speed for 5–7 min,
and the maximum oxygen consumption was calculated from the
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Journal of Experimental Biology
List of symbols and abbreviations
RESEARCH ARTICLE
Journal of Experimental Biology (2017) 220, 582-587 doi:10.1242/jeb.151019
slope of the decrease in oxygen concentration. To check for other
possible sources of oxygen consumption during all measures of
oxygen consumption, the oxygen concentration of an empty
chamber was measured, and when necessary oxygen consumption
by the empty chamber was subtracted from the fish data. All
respirometers were dried after use and regularly cleaned so that
confounding effects were minimal. Metabolic scope was calculated
as the difference between maximum and resting metabolic rate.
and flow treatment (flowing water and still water) as fixed factors to
test the effects of UV-B and flow on swimming performance,
metabolic rate, GSH concentration, CAT activity, SOD activity,
lipid peroxidation and protein carbonyl concentration. We used
standard length as a covariate in the analysis of Ucrit, and mass as a
covariate in the analysis of oxygen consumption. A significance
level of 0.05 was used for all analyses, and the data are presented as
means±s.e.m.
ROS damage: protein carbonyl and lipid peroxidation
RESULTS
Swimming performance and metabolic rate
To measure ROS-induced damage, fish were killed by immersion in
a buffered MS222 solution (0.4 g l−1; Sigma-Aldrich, Castle Hill,
NSW, Australia) and tail muscle was dissected and stored at −80°C
for biochemical assays. Lipid peroxidation was measured in tail
muscle of seven fish from each treatment group using a commercial
kit (MAK085, Sigma-Aldrich) and following the manufacturer’s
instructions. The lipid peroxidation assay is based on measuring
malondialdehyde (MDA), the end product of the lipid peroxidation
chain, and the amount of lipid peroxidation in each sample was
expressed as nmol MDA per mg tissue.
Protein carbonyl concentration was determined in tail muscle of
seven fish from each treatment group using a commercial kit
(MAK094, Sigma-Aldrich) and following the manufacturer’s
instructions. The protein carbonyl assay is based on measuring a
stable carbonyl group formed as a result of ROS-oxidised proteins.
The amount of protein carbonyl in each sample was reported as
nmol protein carbonyl per mg total protein. To determine the
concentration of total protein, a bicinchoninic acid protein assay kit
(BCA1 and B9643, Sigma-Aldrich) was used following the
manufacturer’s instructions.
Flowing water significantly increased Ucrit of fish in both UV-B and
no-UV-B control treatments (main effect of flowing water; Table 1,
Fig. 1A). There was a significant main effect of UV-B on sustained
swimming performance, where fish exposed to UV-B had
significantly lower Ucrit than fish not treated with UV-B (Table 1,
Fig. 1A).
There was no effect of UV-B or water flow on resting metabolic rate,
maximum metabolic rate or metabolic scope (Table 1, Fig. 1B–D).
ROS damage: protein carbonyl and lipid peroxidation
Fish exposed to UV-B had significantly higher lipid peroxidation
and protein carbonyl concentration than control fish (main effect of
UV-B; Table 1, Fig. 2). Protein carbonyl concentration was
significantly lower in UV-B-exposed fish living in flowing water
(significant flow×UV-B interaction; Table 1, Fig. 2B). Fish kept in
flowing water also had significantly decreased lipid peroxidation in
both UV-B and control groups (main effect of flowing water;
Table 1, Fig. 2A).
Antioxidants: GSH, SOD and CAT
The concentration of total GSH was determined in tail muscle of
nine fish from each treatment using a commercial kit (CS0260,
Sigma-Aldrich) and following the manufacturer’s instructions.
Reduced glutathione (GST) is the main form of GSH present inside
cells. GST stabilises ROS by donating an electron, which leads to
the formation of glutathione disulphide (GSSG). The level of GSH
in each sample was reported as nmol GSH per mg tissue.
CAT enzyme activity was determined in tail muscle of nine fish
from each treatment group and according to published protocols
(Barata et al., 2005; Yakovleva et al., 2004). Tissues were
homogenized in 1:9 (w/v) 100 mmol l−1 phosphate buffer
( pH 7.4) containing 100 mmol l−1 KCl and 1 mmol l−1 EDTA,
and homogenates were centrifuged at 4°C for 10 min at 10,000 g.
The supernatant was used to measure CAT activity in an assay
medium containing 50 mmol l−1 phosphate buffer ( pH 7.8) and
30% H2O2. The reaction was monitored for 3 min at 240 nm and the
CAT activity was reported as µmol of substrate converted into
product per minute (=1 unit) per mg tissue.
The activity of total SOD (Cu/Zn, Mn and FeSOD) was
determined in tail muscle of nine fish from each treatment group
using a commercial kit (706002, Cayman Chemicals, MI, USA) and
following the manufacturer’s instructions; 1 U of SOD is defined as
the amount of enzyme needed to exhibit 50% dismutation of the
superoxide radical, and the SOD activity in each sample is reported
as units per mg tissue.
Statistical analysis
Data were analysed by permutational analysis of variance in the
package lmPerm in R. We conducted a two-factor permutational
analysis of variance with UV-B treatment (UV-B and no-UV-B)
584
Fish from the flowing water treatments had significantly higher
CAT activity and GSH concentration in both UV-B and control
groups compared with fish from the still water treatments (main
effect of flowing water; Table 1, Fig. 3A,B). However, fish from the
UV-B treatment groups showed significantly reduced CAT activity
and GSH concentration (main effect of UV-B; Table 1, Fig. 3A,B).
There was no effect of UV-B or water flow on SOD activity
(Table 1, Fig. 3C).
DISCUSSION
We show that fish living in flowing water had increased antioxidant
defences, reduced oxidative damage and increased swimming
Table 1. Results from two-way permutational analyses of variance
P
Ucrit
Resting Ṁ O2
Maximum Ṁ O2
MS
MDA
PC
CAT
GSH
SOD
d.f.
UV-B
Flow
UV-B×flow
1,43
1,33
1,33
1,33
1,24
1,24
1,32
1,32
1,32
<0.001*
0.91
0.25
0.22
<0.001*
<0.001
<0.001*
0.038*
0.25
<0.001*
0.34
0.98
0.98
0.002*
0.71
<0.001*
0.030*
0.88
0.15
0.49
0.73
0.56
0.18
0.027*
0.19
0.27
0.88
Analyses of variance were used to test the effects of water flow and UV-B
radiation (UV-B) on critical sustained swimming performance (Ucrit), resting
metabolic rate (Ṁ O2), maximum metabolic rate, metabolic scope (MS), lipid
peroxidation (MDA), protein carbonyl (PC), catalase (CAT) activity, glutathione
(GSH) concentration and superoxide dismutase (SOD) activity. An asterisk
indicates a significant result.
Journal of Experimental Biology
Antioxidants: GSH, SOD and CAT
Ucrit (BL s–1)
a
10
*
8
*
6
.
4
2
0
.
1.0
0.4
0.2
0
1.0
0.6
0.4
0.2
0
6
Flowing water
Still water
0.6
UV-B
C
0.8
B
0.8
Control
Metabolic scope
(µmol min–1 g–1)
Maximum MO2 (µmol min–1 g–1)
UV-B
1.0
Control
D
0.8
0.6
0.4
0.2
Control
UV-B
Control
Fig. 1. Effect of ultraviolet B radiation (UV-B) and water flow on swimming
performance and metabolic rate. (A) Flowing water significantly increased
critical sustained swimming speed (Ucrit) compared with still water treatment in
both UV-B and control groups, but fish exposed to UV-B showed significantly
lower Ucrit than control fish. There was no effect of UV-B or water flow on resting
metabolic rate (Ṁ O2; B), maximum metabolic rate (C) and metabolic scope (D).
An asterisk indicates significant differences between flowing and still water
treatments. Horizontal lines and letters above bars indicate significant
differences between UV-B and control groups. Swimming performance was
measured in 12 fish per treatment and metabolic rate in 8–10 fish per
treatment. Means+s.e.m. are shown.
performance when exposed to UV-B. Hence, there is a ‘transfer’ of
benefit across responses to different environmental stimuli. This
finding is interesting because it shows that the mechanistic link
between different habitat characteristics can determine ecological
success of animals. Locomotor performance is closely related to
fitness (Husak, 2006; Le Galliard et al., 2004), so the increase in
sustained locomotion is likely to have important ecological
consequences. Relative locomotor performance of predator and
prey, for example, determines predation success (Grigaltchik et al.,
2012), and therefore UV-B-induced decreases in locomotor
performance increase the likelihood of being captured by
predators and, vice versa, any increases in prey performance
should increase survival.
UV-B reduced Ucrit in fish in both flowing and still water but, as
we hypothesised, fish exposed to UV-B had significantly higher
Ucrit in flowing water than in still water. This result indicates that the
increased antioxidant capacities resulted in reduced ROS damage
and increased Ucrit. Interestingly, fish exposed to UV-B in flowing
water had similar swimming performance to control fish in still
water. Water flow thereby negated the negative effects of UV-B.
However, despite increased defences and reduced damage, UV-B
still reduced exercise-enhanced locomotor performance.
Contrary to our hypothesis, metabolic scope was not affected by
UV-B or exercise. It would have been expected that sustained
exercise increases maximal oxygen consumption rate (Joyner and
Coyle, 2007). However, it may be that the intensity of exercise in our
treatments was not high enough to enhance maximal metabolic rate.
Our results showing that Ucrit increased in the absence of an increase
8
Flowing water
a
B
Still water
4
*
b
2
*
6
a
*
b
4
2
0
0
UV-B
0
UV-B
A
Control
UV-B
Control
Fig. 2. Effect of UV-B and water flow on ROS-induced damage. Fish
exposed to UV-B showed significantly higher lipid peroxidation (A) and protein
carbonyl concentrations (B) than fish not treated with UV-B. However, there
was a main effect of flowing water on lipid peroxidation, where fish in flowing
water had significantly lower lipid peroxidation than fish in still water in both
UV-B and control groups (A). Protein carbonyl concentration was significantly
lower in flowing water for fish exposed to UV-B (UV-B×flow interaction; B).
An asterisk indicates significant differences between flowing and still water
treatments. Horizontal lines and letters above bars indicate significant
differences between UV-B and control groups. Lipid peroxidation and protein
carbonyl concentrations were measured in 7 fish per treatment. Means+s.e.m.
are shown.
in maximal metabolic rate and metabolic scope indicate that
sustained performance is relatively independent from mitochondrial
ATP supply. Exercise can also increase locomotor performance by
improving muscle efficiency – that is, the amount of oxygen used
for a given amount of force produced (Joyner and Coyle, 2007;
Lichtwark and Wilson, 2005; Salin et al., 2015). Additionally,
exercise can alter contractile properties and fatigue resistance by
modulating calcium cycling dynamics and fibre-type composition
(Anttila et al., 2008; Gundersen, 2011; Place et al., 2015). Calcium
cycling dynamics, in particular, are important in determining force
production and fatigue resistance, and hence swimming
performance (Gundersen, 2011). Fast release of calcium from the
sarcoplasmic reticulum increases force production but decreases
fatigue resistance (Seebacher et al., 2012). Increased rates of resequestration of calcium into the sarcoplasmic reticulum by the
sarco(endo)plasmic reticulum ATPase (SERCA) improves both
sprint and sustained locomotion (Seebacher and Walter, 2012). ROS
can interfere with calcium release dynamics from the sarcoplasmic
reticulum and the calcium sensitivity of troponin (Cheng et al.,
2016). Hence, UV-B-induced ROS may reduce swimming
performance by interfering with calcium cycling dynamics,
although we have shown previously that UV-B did not affect
SERCA activity in mosquitofish (Ghanizadeh Kazerouni et al.,
2015).
In humans, chronic exercise caused similar increases in
antioxidant capacities and reduced ROS damage, and one of the
recognised benefits of regular exercise is that it reduces oxidative
stress (Gram et al., 2015; Radak et al., 2013). Our results indicate
that the transfer of the increased antioxidant capacity to improve
resilience to the negative effects of UV-B radiation is an additional
benefit of regular exercise beyond its direct health-promoting effects
(Booth et al., 2012; Hawley and Holloszy, 2009; Joseph et al.,
2016). At an ecological level, our findings indicate that fish from
streams that experience greater levels of physical activity are more
resilient to UV-B. Alterations to flow regimes of rivers and streams
therefore may have pronounced effects on the resilience of animals
to UV-B and their fitness. Local weather patterns and regional and
585
Journal of Experimental Biology
b
Protein carbonyl
(nmol mg–1 protein)
A
12
Lipid peroxidation
(nmol MDA mg–1 tissue)
14
Journal of Experimental Biology (2017) 220, 582-587 doi:10.1242/jeb.151019
Resting MO2 (µmol min–1 g–1)
RESEARCH ARTICLE
RESEARCH ARTICLE
Journal of Experimental Biology (2017) 220, 582-587 doi:10.1242/jeb.151019
0.6
b
a
0.1
*
*
B
0.04
b
a
*
0.4
*
0.2
0
0
UV-B
Control
UV-B
Control
SOD activity (U mg–1 tissue)
A
GSH (nmol mg–1 tissue)
CAT activity (U mg–1 tissue)
0.2
C
Flowing water
Still water
0.03
0.02
0.01
0
UV-B
Control
global climate patterns, such as El Nino and climate warming, can
interact to alter rainfall and thereby flow rates of water bodies
(Helmuth et al., 2014; Mol et al., 2000). Human modifications such
as the construction of dams will compound climate effects and also
cause interactions between flow and other drivers such as
temperature (Macnaughton et al., 2016). We show that decreased
flow, as well as changes in temperature (Ghanizadeh Kazerouni
et al., 2016) can make fish more vulnerable to the negative effects of
UV-B.
In conclusion, exposure to water flow increased resistance to the
deleterious effects of UV-B while simultaneously enhancing
locomotor capacity, which may promote fitness gains relative to
sedentary individuals in still water. It is therefore possible that a
decrease of water flow because of environmental changes results in
reduced regular physical activity and antioxidant capacity, which
exacerbates the negative effects of UV-B on performance and fitness.
Competing interests
The authors declare no competing or financial interests.
Author contributions
F.S. and C.E.F. conceived the ideas, F.S. designed the experiments and wrote the
manuscript, E.G.-K. conducted the experiments, and E.G.-K. and C.E.F. revised the
manuscript.
Funding
This research was funded by an Australian Research Council Discovery Grant
(DP140102773) to F.S. and C.E.F. E.G.-K. was supported by an Australian
Government International Postgraduate Research Scholarships (IPRS).
Data availability
Data are available from the Dryad Digital Repository (Ghanizadeh-Kazerouni et al.,
2017): http://dx.doi.org/10.5061/dryad.4g200
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